On Telegraph Hill there is an engineering challenge. What can be done to protect people and property from falling rocks and mud? It happened Monday, it's happened before, and it will probably happen again.

There's no certain solution. The good news is the repair work is coming along and 13 truckloads of rocks have been removed so far. The owners of three yellow-tagged homes have been allowed to go back inside at least for a short time.

The bad news is that with a hill made of crumbling, cracked, condensed sand, you haven't heard the last of slides on Telegraph Hill. It's the case of a crumbling cliff that has begun to sound like a broken record.

Neighbor Mary Fenton doesn't worry about the hill because the city of San Francisco does after boulders and debris plunged down the cliff last Monday, crushed a car, and forced the Department of Public Works to yellow tag three units. On Wednesday, the clean-up continued without promises.

When Mohammad Nuru from the Department of Public Works was asked when was the next time the hill could fall, he said, "I don't know, but as we speak, we still have loose rocks rolling down the hill."

It looked like a quarry on Wednesday and 100 years ago, that exactly what it was when George and Harry Gray dug up the crushed, cracked, condensed sand for use as ballast on ships. This is not ideal building material, according to Win Bryson, an architect who lives in the impacted building, and found an old picture of the hill before vegetation moved in.

"Geologically, it looks precarious," said Bryson.

History reinforces that idea. There was a landslide in 1992 and another from 2007. And there have been numerous other slides in between. The city says it will spend about $2 million on this one, and expects a financial contribution from management at 240 Lombard. Their representatives were not talking Wednesday.

"There has been dialogue over many years with the property owners and the city and so we will be going back to the table to have that discussion to figure out exactly how that gets covered," said Nuru.

One last note -- if the cliff and building look vaguely familiar, there is a good reason. Two weeks ago, on that very same cliff, San Francisco police launched a 24 hour manhunt for an accused burglar who said his name was "Dan." Eventually, he got away. Public Works does not blame Dan for the slide. Rainwater seeping into cracks and weighing down the hill did.